This invention relates to a brush and terminal assembly for an engine starter.
FIG. 1 illustrate one example of a conventional coaxial engine starter. The illustrated coaxial engine starter comprises a dc motor 1 having a hollow armature rotary shaft 2 defining an inner bore 2a therein and a solenoid switch 3 disposed at the rear end of the dc motor 1. The solenoid switch 3 has a plunger rod 3a which supports a push rod 4 extending into the inner bore 2a of the armature rotary shaft 2. The coaxial engine starter also comprises an output rotary shaft 5 coaxially disposed at the front end of the armature rotary shaft 2. The output rotary shaft 5 has its rear end inserted into the inner bore 2a of the armature rotary shaft 2 and abuts at its inserted rear end with the front end of the push rod 4 within the armature rotary shaft 2 so that the output rotary shaft 5 may be moved forward when the plunger rod 3a of the solenoid switch 3 is electromagnetically pushed forward.
In the coaxial engine starter, a commutator 6 is mounted at the rear portion of the armature rotary shaft 2, and the commutator 6 is slidably contacted by a plurality of brushes 9 supported by brush holders 8 mounted to a mounting plate 7 to constitute a commutator assembly. At the rear end of the commutator assembly and in front of the solenoid switch 3, there is mounted a terminal assembly 12 in which two terminal bolts 10 and 11 are resin molded as shown in FIG. 2. On one side of this terminal assembly 12, two stationary contacts 14 and 15 which can be connected to each other by a movable bridging contact 13 of the solenoid switch 3 are provided. These stationary contacts 14 and 15 are formed integral with and electrically connected to the terminal bolts 10 and 11.
As shown in FIG. 3, the terminal bolt 10 is connected to a battery B mounted on a vehicle by a line 16, and the terminal bolt 11 is connected to the positive brushes 9 by a line 17 and to a solenoid coil 18 of the solenoid switch 3.
In FIG. 1, a pinion 19 is mounted on the front end of the output rotary shaft 5 and is capable of engaging and disengaging an engine ring gear (not shown) by reciprocating motion of the output rotary shaft 5, a planetary speed reduction gear 20 is provided for reducing the rotational speed of the armature rotary shaft 2, and an over-running clutch 21 is provided for transmitting the speed-reduced rotation of the planetary speed reduction gear 20 to the output rotary shaft 5 and for preventing the rotation of the output rotary shaft 5 to be reverse-transmitted to the dc motor 1.
However, with the above-described coaxial engine starter, the brush holder mounting plate 7 and the terminal unit 12 which constitutes the commutator of the dc motor 1 are formed as separate components, so that the brush holder mounting plate 7 must first be installed on the rear end of the yoke 1a of the dc motor 1 and must be held by the rear bracket 1b, and thereafter the terminal unit 12 and the solenoid switch 3 are disposed in the named order on the rear portion of the rear bracket 1b and then the solenoid switch 3 is secured by the bolt 22 to the front bracket 1c. Therefore, the assembly is very troublesome and many wirings are placed outside of the outer circumference of the machine frame, impeding easy installation of the starter to the engine because the electrical connection between the positive side brush 9 and one of the stationary contacts 14 must be achieved by connecting the lead conductor 17 from the brush 9 to the terminal bolt 10 projecting outwardly from the starter machine frame, and the lead-out portion of the current coil 18 of the solenoid switch 3 must also be connected to the terminal bolt 10. Moreover, even though the coaxial starter is designed so as to simplify the configuration of the starter into a generally cylindrical shape in order to make lay-out design of the engine compartment of the vehicle easier and more efficient, the above-mentioned two terminal bolts projecting out from the machine frame degrade the easiness and the efficiency of the lay-out design.